The invention relates to a sheet transfer device which can be reset according to the size of printed sheets and which achieves accurate registration on printing machines for one and two sided printing.
The present device achieves automatic size resetting on the turning and transfer drum without affecting the registration accuracy. The reset wheel of the transfer drum performs the function of the gripping device drive wheel which stretches the sheets on the transfer drum.
Registration of two sided printing depends on the sheet transfer drum, accuracy, i.e., the way of sheet turning.
The invention is an attachment for performing sheet transfer from the transfer to the turning drum during printing accurately and consistently. In this way, a high registration accuracy in two-sided printing may be achieved.
Moreover, the invention is a reset wheel which makes it possible to eliminate production inaccuracies and to reset it to be accurately centric with the transfer drum axis.
The reset wheel is designed in a way to ensure its easy resetting, according to the size of the printed sheets, with the ability to take up clearances. Setting up according to the size of printed sheets and the centricity of reset gear rim can be accomplished independently.
One of the known devices is arranged in such a manner that when resetting the printing machine for change of printed sheet size in two sided printing, it is necessary to reset the transfer drum and the turning roll separately. At the same time, the coherent mechanisms are to be reset, too.
A disadvantage of this attachment is that it necessitates that each mechanism be reset independently. Inaccuracies can arise by not resetting the same value on the transfer and turning drum according to the size of printed sheets.
Another known device comprises a transfer drum having a reset wheel attached to the gripping device for stretching and transferring of sheets by means of carrying pins.
The reset wheel engages the turning drum gear and resetting of transfer and turning drum is done at the same time.
A disadvantage of the device is that it neither allows for adjustment of the reset wheel centricity, nor enables setting up of clearance between the supporting flange and the reset gear. Another disadvantage is the inability to take up the reset wheel clearance.
A printing machine having two printing units and transfer and turning cylinders is described in U.S. Pat. No. 3,829,084, the contents of which are incorporated herein by reference.